1. Field of the Invention
The present invention pertains to a system and method for controlling liquid slug flow in multi-phase fluid pipelines, particularly in oil and gas production facilities.
2. Background
In the production of oil and gas from subterranean wells, a long-standing problem is that of dealing with the two-phase flow (gas and liquid) of the produced fluid which may vary considerably during the production life of a well or a group of wells whose flow is commingled in a common production flowline. Late in the life of an oil-bearing formation, for example, there may be substantial production of gas along with the production of hydrocarbon liquids, particularly if gas is being used as a drive fluid to force crude oil to the production well or wells. This two-phase flow often results in so-called slug flow wherein "slugs" of liquid occur in the flowlines which are connected to the separation, treatment and pumping equipment. Accordingly, this equipment must be sized initially to accommodate the slugs or the fluid handling facilities must be modified at some point during the life of a production field to accommodate the increased slug flow. Since the conventional approach to managing slug flow is based primarily on the prediction of maximum slug flow conditions, this usually leads to over-designing facilities.
U.S. Pat. No. 5,256,171, issued Oct. 26, 1993 Richard L. Payne and assigned to the assignee of the present invention, describes and claims one type of slug flow mitigation system for a production well fluid gathering system. It has been considered desirable to develop a slug flow mitigation system and method which does not require modification to existing facilities and which may take advantage of the capacity of a flowline itself to mitigate slug flow. Moreover, in developing remotely located and economically marginal oil and gas fields or for extending the development of an existing field, the costs associated with managing slug flow can result in such fields being declared unproductive. Accordingly, an inexpensive and easily retrofitted slug mitigation system and method is particularly attractive for keeping mature oil and gas production fields in production. It is to these ends that the present invention has been developed with a view to providing a system and method which utilizes existing facilities with only minor modifications to provide for controlling slug flow in gas and oil production flow facilities, in particular.